The present invention relates to a valve timing control device for controlling the opening and closing timing of an intake or exhaust valve in an internal combustion engine.
It is herein noted that, in the following description, the terms “front”, “rear” and other orientational expressions are used to facilitate the description of a valve timing control apparatus and are not intended to limit the structure of a valve timing control apparatus to any particular position or orientation.
Japanese Laid-Open Patent Publication No. 2011-226372 discloses a valve timing control apparatus for controlling the opening and closing timing of an engine valve in an internal combustion engine. The valve control apparatus includes an electric motor accommodated in a motor housing, a cover member attached to a front side of the motor housing, with a predetermined clearance left between the motor housing and the cover member, and a pair of power-supply slip rings fixed to an inner side of the cover member at positions facing the clearance. The electric motor has a power-supply plate fixed at a front end portion of the motor housing and a power-supply brush held on the power-supply plate in sliding contact with the power-supply slip rings to supply power to a coil of the electric motor via the power-supply slip lings. The valve control apparatus further includes a magnetic sensor disposed between an output shaft of the electric motor and a motor-side portion of the cover member to detect a rotational angle of the motor output shaft. The magnetic sensor has a magnetic rotor provided with six targets on the front end portion of the motor output shaft and a Hall element detector provided in the cover member to retrieve a pulse signal through the six targets of the magnetic rotor such that that the rotational angle of the motor output shaft can be detected according to the pulse signal. By the adoption of such a configuration, the variable valve control apparatus controls the relative rotational phase of crankshaft and camshaft based on the rotational angle of the motor output shaft so as to improve the stability and response of control of the valve timing while reducing the consumption energy of the internal combustion engine.